To select the ideal water tank for the operation, it is important that waste facilities carefully consider all aspects of water tank design—including shape, baffling, water movement and ease of maintenance.
By Josh Swank
Water is an essential component in waste operations, and how it is hauled and applied can significantly impact an operation’s overall productivity and safety. Though water trucks appear basic, several factors of tank design have a significant impact on efficiency. From the challenges of water movement in the tank and its effect on overall stability, to the steel used in the construction, key elements of tank design directly affect uptime, maintenance, efficiency and safety.
To select the ideal water tank for the operation, it is important that waste facilities carefully consider all aspects of water tank design—including shape, baffling, water movement and ease of maintenance. After all, the right equipment choice could decrease cycle times by as much as 25 percent, while the wrong choice could lead to wasted time and resources.
A Square Deal
Stability is one of the key challenges waste operations must overcome with any equipment investment. Landfills have few hard surfaces or established roads, and none in active dumping areas, leaving drivers to navigate a constantly changing landscape of soft footing. Even seasoned operators cannot anticipate when soft, uneven refuse mounds will sink or give away. This uneven footing created by the irregular density of the refuse material can cause a truck to tip or roll, resulting in injuries and equipment damage. To minimize the risk to employees and equipment, the tank’s center of gravity and overall stability must be a top concern during the design process.
When it comes to water tanks, a round design is most common. However, this design has one major drawback—the tank’s curved sides raise the water’s center of gravity, decreasing stability. In some cases, operators will avoid filling their tanks completely to mitigate the instability. However, this leads to more frequent filling, contributing to added downtime and increased fuel consumption as they backtrack to the water source.
Additionally, rounded tank designs contribute to water churning since there are no corners, edges or obstructions to slow the water’s momentum. This constant, and sometimes rapid, water movement poses a safety risk for the driver and people nearby since the water can shift the center of gravity and cause the truck to become unstable.
Alternatively, water tanks with square corners minimize churning and have a larger capacity by simply not rounding off the sides of the tank. This added capacity is closer to the ground, which provides a lower Center of Gravity (CoG). They also maximize productivity and operator safety due to their box-shaped structure, water baffles and water metering systems. This style design lowers the unit’s overall center of gravity, enhancing stability and allowing drivers to safely fill the tank to capacity. The box-shaped structure makes it possible to haul up to 20 percent more water than rounded tanks, resulting in considerable time and cost savings.
For example, an operation may have two, on-highway haul trucks with 5,000-U.S. gallon rounded tanks in its fleet with a dump rate of 500 gpm. Each truck works eight hours per day and sprays about one load per hour—20 minutes for spraying and 40 minutes driving back and forth to the water source. By the end of each day, this water tank fleet would spray 80,000 gallons of water.
A waste operation running off-highway trucks with 9,000-U.S. gallon square-cornered tanks can cover a much larger area with minimal backtracking. This is partly because each of the squared water tanks holds close to the truck’s true hauling capacity. The truck drivers in this example now can fill the tanks to capacity. These tanks also feature a much higher dump rate of up to 1,500 gpm—allowing a full dump in just six minutes. So, while they still have to travel 40 minutes to and from the water source, they are able to decrease cycle times by 25 percent, meaning each truck can make an additional two to three trips in an eight-hour shift. By the end of the day, this water tank fleet has sprayed around 169,600 gallons of water.
In addition to increased capacity and faster cycle times, advanced water tank distribution systems that offer operators complete control over water output provide maximum efficiency—and safety—on applications throughout the landfill.
For instance, individually controlled spray heads help water truck drivers optimize their water usage. Inside the cab, operators can turn on the individual spray heads—and in some systems, program a spraying interval. This optimizes water usage, so operators cover more surface area. Additionally, the added control and metering means they spend less time backtracking to a wellhead than a truck with a traditional water tank control system.
Water truck drivers also need to concentrate on their surroundings to ensure their safety as well as the safety of others. In addition to soft footing, they must also be aware of other employees and equipment in the immediate area. Taking attention off the task at hand can significantly increase the risk of an accident, especially when operating heavy-duty off-highway equipment. Components, such as simple water metering controls, also contribute to overall safety by allowing the water truck driver to better focus on his or her surroundings while driving.
Bafflingly High Safety
A water tank’s internal baffling system is another key element that affects safety and efficiency. Baffles inside the tank help minimize water from surging side-to-side and front-to-back. Almost all water tanks feature baffles, but many have large holes cut out to provide maintenance personnel access to the individual compartments. These openings allow water to surge between compartments, limiting surge protection and increasing the risk of the truck tipping or being involved in another type of accident.
To minimize surging, some tanks feature sophisticated water flow control systems that use baffling that runs from floor to ceiling as well as along the complete length and width of the tank, resulting in full compartmentalization of the water. Within the outer compartments, some manufacturers install side-surge stabilizers along the walls to prevent water from rolling or churning. The number of compartments can vary between tanks.
For the best level of water compartmentalization, these baffles have areas that allow water to flow freely throughout the tank, but are small enough to prevent water from surging during use. Water tanks featuring access doors that are about as tall as an average-sized worker provide a more civilized and advanced solution than simply a hole near the ground in the baffle walls that a worker would have to crawl through. These baffle doors, which technicians walk through easily, practically eliminate the need to crouch down while they maintain the tank, and the doors remain shut while the water tank is in operation, suppressing water surge. With access between multiple compartments, technicians have minimal concerns about working within the tank, as the internal and external access doors, when open, minimize confined space concerns that are present with traditional tanks that do not feature such advanced technology.
To allow technicians into the tank for maintenance, some manufacturers incorporate external doors, which can provide fresh air and natural light throughout the tank after opening all of the external and baffle doors. When the tank is empty and the inside needs servicing, technicians simply enter the tank and open the internal baffle doors. This system offers load stability as well as easy service and maintenance, allowing technicians to access the inside of the tank safely and easily, instead of putting off the difficult work for later.
Safety and efficiency are not the only concerns during operation. Ease of maintenance is often an overlooked component when it comes to water tanks. Here again, a square design offers several benefits that not only keep workers safe, but also allows them to perform tasks more efficiently. A tank with a flat top, for example, reduces the likelihood of slipping and falling when filling or servicing the truck. This risk can be further abated with lanyard tie-offs to provide an anchor point for operators.
Access to the tank’s interior is crucial in order to complete routine maintenance, such as clearing out sediment and debris that builds up over time. This can be a significant challenge with some tank designs. With many tanks, the only access point is through the fill hole on the top. The alternative is to cut a hole in the side of the tank using an acetylene torch. This causes unnecessary downtime and creates sharp edges for those entering the tank to maneuver and requires a repair job after the maintenance is complete.
Alternatively, enhanced water tank designs eliminate this hassle and safety hazard by incorporating as many as three external access doors on both the front and back of the tank. When opened, the doors allow personnel to easily enter the tank and, with the aid of the baffle doors, have natural airflow and lighting for truck maintenance.
Perhaps the best way prevent accidents during maintenance is to invest in a design that minimizes the need for maintenance and makes those tasks as simple as possible. For instance, some manufacturers use 450 Brinell steel—some of the hardest and most durable steel on earth—to achieve a long service life for the water tank. Additionally, with advances in steel technology, some manufacturers offer water tanks that feature materials specially formulated to provide an optimized life in high-acid environments. This drastically slows down the oxidation process, allowing the full hardness of the material to counteract wear. In this way, waste operations with acidic water are able to operate water tanks that use a thinner plate without jeopardizing the unit’s service life. As an added benefit, the thinner plate lowers the overall weight of the truck to save on fuel and reduces CO2 emissions.
Mechanical pipe joining systems are another way that manufacturers make water tank maintenance easier. This system allows mechanics to replace damaged piping easily by removing the coupling’s collar, replacing the pipe and tightening the collar to form a complete seal. This system effectively eliminates the need to weld on a rusty pipe, which can often take hours and equate to substantial downtime for the water truck.
Other innovations feature hydraulic-powered water pumps that drivers can activate while the engine runs at any rpm, using new advances in hydraulic soft-start, soft-stop valving, whereas most require a low rpm rate. This virtually eliminates the risk of overpowering a water pump, which is costly to replace.
Do Not Cut Corners on Productivity and Safety
Water tanks might not seem all that complicated to the outside observer, but savvy waste operations know the most productive, longest lasting machines are those designed to meet the unique challenges of their site. This might drive up the initial cost, but over decades of use, investing in high-quality, low maintenance equipment more than pays for itself with increased safety and productivity. So, rather than trying to fit a round peg into a square hole, look to partner with manufacturers that provide custom solutions.
Josh Swank is Vice President of Sales and Marketing for Philippi-Hagenbuch, has been with the company for more than 20 years and oversees the global sales team. Outside of Philippi-Hagenbuch, he participates in multiple industry and philanthropic organizations, including the National Stone Sand and Gravel Manufacturers & Services Board, the NSSGA Young Leaders and the National Mining Association Board of Governors. He is a trustee of the JWAS Foundation and active within the Peoria, IL, startup community.
Engineering innovative haul-truck solutions for over 50 years, Philippi-Hagenbuch Inc., located in Peoria, IL, has been building equipment for off-highway haul trucks since 1969. During this time they have become a global leader in off-highway truck customization. In addition to their innovative tailgates, push blocks, rear-eject bodies and trailers, Philippi-Hagenbuch designs and builds end-dump bodies, trailers, sideboards, load ejectors and water tanks for nearly every make and model of articulated and rigid frame off-highway truck available. For more information visit www.philsystems.com.